.45 ACP
The .45 ACP (11.43x23mm) (Automatic Colt Pistol), also known as .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the US Army in 1911. __FORCETOC__ Design and history The US Cavalry had been buying and testing various handguns in the late 1890s and early 20th century. The .45 Colt Single Action Army (SAA) had largely been replaced, even by some double action versions of the same. The Cavalry had fielded some double action revolvers in .38 Long Colt. They determined the .38 caliber round was significantly less effective against determined opponents, such as the warriors encountered in the Moro Rebellion of the Philippine-American War, than the .45 Colt. The current issue rifle at the time, the .30-40 Krag, had also failed to stop Moro warriors effectively; the British had similar issues switching to the .303 British, which resulted in the development of the dum-dum bullet. This experience, and the Thompson-LaGarde Tests of 1904 led the Army and the Cavalry to decide a minimum of .45 caliber was required in the new handgun. Thompson and Major Loise Anatole LaGarde of the Medical Corps arranged tests on cadavers and animal remains in the Chicago stockyards, resulting in finding the .45 was the most effective pistol cartridge. They noted, however, training was critical to make sure a soldier could score a hit in a vulnerable part of the body. Colt had been working with Browning on a .41 caliber cartridge in 1904, and in 1905 when the Cavalry asked for a .45 caliber equivalent, Colt modified the pistol design to fire an enlarged version of the prototype .41 round. The result from Colt was the Model 1905 and the new .45 ACP cartridge. The original round that passed the testing fired a 200-grain bullet at 900 ft/s, but after a number of rounds of revisions between Winchester Repeating Arms, Frankford Arsenal, and Union Metallic Cartridge, it ended up using a 230 grain bullet fired at about 850 ft/s. The resulting .45-caliber cartridge, named the .45 ACP, was similar in performance to the .45 Schofield cartridge, and only slightly less powerful (but significantly shorter) that the .45 Colt cartridges the Cavalry was using. By 1906, bids from six makers were submitted, among them Browning's design, submitted by Colt. Only DWM, Savage, and Colt made the first cut. DWM, which submitted two Parabellum P08s chambered in .45 ACP withdrew from testing after the first round of tests, for unspecified reasons. One of the DWM pistols, serial number 1, was destroyed in testing; the remaining example, serial number 2, is one of the most desirable collectors' handguns in existence. In the second round of evaluations in 1910, the Colt design passed the extensive testing with no failures, while the Savage design suffered 37 stoppages or parts failures. The resulting weapon was adopted as the Model 1911. The cartridge/pistol combination was quite successful but not satisfactory for US military purposes. Over the next few years a series of improved designs were offered, culminating in the adoption in 1911 of the "Cal. .45 Automatic Pistol Ball Cartridge, Model of 1911", a 1.273 in long round with a bullet weight of 230 grains. The very first production, at Frankford Arsenal, was marked "F A 8 11", for the August 1911 date. The cartridge was designed by John Browning of Colt, but the most influential person in selecting the cartridge was Army Ordnance member Gen. John T. Thompson. Thompson insisted on a real "man stopper" pistol, following the poor showing of the Army's .38 Long Colt pistols during the Philippine-American War (1899-1902). Cartridge dimensions The .45 ACP has 1.62 ml cartridge case capacity. The common rifling twist rate is 406mm, 6 grooves, land width = 3.73mm and the primer type is large pistol. The cartrdige headspaces on the mouth of the case at the L3 datum reference. According to the official C.I.P. guidelines, the .45 ACP case can handle up to 130 MPa piezo pressure. In C.I.P. regulated countries every pistol cartridge combo has to be proofed at 130% of this maximum pressure to certify for sales. The SAAMI pressure limit for the .45 ACP is set at 21,000 psi piezo pressure, while the SAAMI pressure limit fof the .45 ACP + P is set at 23,000 psi. Performance The .45 ACP is an effective combat pistol cartridge that combines accuracy and stopping power for use against human targets. The cartridge also has relatively low muzzle blast and flash, as well as moderate recoil. The .45 ACP also operates at a relatively low maximum chamber pressure, which due to a low bolt thrust helps extend service life of weapons in which it is fired. Like many pistol cartridges, it is a low-velocity round and thus ineffective against body armor. Another drawback for large scale military operations is the cartridges size, weight, and the increased material cost of manufacture compared with the smaller 9x19mm Parabellum cartridge. Even in its non-expanding full metal jacket version, the .45 ACP cartridge has a reputation for effectiveness against human targets because its large diameter creates a deep and substantial permanent wound channel which lowers blood pressure more rapidly. Bullet energy for the .45 ACP loads varies from roughly 350 to 400 ft lbf. ATOMIC Ammunition produces a new load that pushes a 185-grain copper bonded hollow point bullet to 1225 fps and achieves over 616 foot pounds of energy. The table below shows common performance parameters for several .45 ACP loads. The .45 ACP's combination of stopping power and controlled penetration makes it practical for police use, although numerous issues, including the resulting decrease in magazine capacity and the larger size and weight of pistols chambered in this caliber, have led more police departments in the USA to adopt sidearms in 9x19mm, .40 S&W, and .357 SIG. With standard (not extended) single-stack magazines, pistols chambered in .45 ACP usually hold 8 rounds or less (an exception to this is the .45 ACP version of the Smith & Wesson SW99, which holds 9). However, many modern versions of .45 ACP handguns have double-stack magazines capable of holding as many as 14 cartridges, such as the HS2000, and the FN FNP-45 Competition and Tactical both hold 15, though this greatly increases the pistol's bulk, and with that lowers maneuverability. Many US tactical police units still use the .45 pistol round, including the FBI's Hostage Rescue Team. While high capacity firearms are available in .45 ACP, the greater length and diameter of the .45 ACP means that the grip of the pistol must be longer and wider than the grip of a comparable pistol of smaller caliber; this increase in grip size can make the pistol difficult to use for shooters with smaller hands. Today, most NATO militaries use sidearms chambered for the 9x19mm Parabellum cartridge, but the effectiveness of the .45 ACP cartridge has ensured its continued popularity with large caliber sport shooters, especially in the US. In addition, select miltary and police units around the world still use firearms firing the .45 ACP. In 1985, the .45 ACP M1911A1 pistol was replaced by the Beretta M9 9mm pistol as the main sidearm of the US military, although select Special Operations units continue to use the M1911A1 or other .45 ACP pistols. Because standard pressure and load .45 ACP rounds fired from handguns or short barreled submachine guns are inherently subsonic, it is one of the most powerful pistol calibers available for use in suppressed weapons, since subsonic rounds are quieter than supersonic rounds. The downside to the use of .45 ACP in suppressed weapons is that increasing the diameter of the passage through a suppressor decreases the suppressor's efficiency; thus, while .45 ACP is among the most powerful suppressed pistol rounds, it is also one of the loudest. Most .45 suppressors must be fired "wet" (with an ablative medium, usually water) to bring down sound levels to a "hearing safe" level. Load variants Several manufacturers parket preloaded .45 ACP rounds in sizes ranging from 117 to 250 grains, with the most popular commercial load being the standard military loading of a 230-grain FMJ bullet at around 850 ft/s. Most ammunition manufacturers also market what are termed "+P" loadings in pistol ammunition, including the .45 ACP. This means the cartridge is loaded to a highter maximum pressure level than the original SAAMI cartridge standard, generating higher velocity and more muzzle energy. In the case of the .45 ACP, the standard cartridge pressure is 21,000 psi and the SAAMI .45 ACP +P standard is 23,000 psi. This is a common practice for updating older cartridges to match the better quality of materials and workmanship in modern firearms. The terminology is generally given as ".45 ACP +P", and appears on the headstamp. It is important to note that +P cartridges have the same externam dimensions as the standard-pressure cartridges and will chamber and fire in all firearms designed for the standard-pressure loadings. However, it should be noted that the inner dimensions of the +P cartridge is different than the standard-pressure cartridge dimensions and thus allows for higher pressures to be safely achieved in the +P cartridge. Popular derivative versions of the .45 ACP are the .45 super and .460 Rowland. The Super is dimensionally identical to the .45 ACP, however, the cartridge carries a developer established pressure of 28,500 psi and requires minor modification of quality firearms for use. The Rowland case is 0.057" longer specifically to prevent it fron being chambered in standard .45 ACP firearms. The Rowland operates at a developer established 40,000 c.u.p. and may only be used within a select group of firearms significantly modified for this purpose. Brass cases for each of these cartridges carry the applicable name within the headstamp. The Super provides approximately 20% greater velocity than the .45 ACP +P; the Rowland approximately 40% greater velocity than the .45 ACP +P. Category:United States Category:U.S. Military